British Patent Specification No. 1 458 399 (English Electric Valve Company Limited) describes a streaking or framing image tube in which two mesh electrodes are interposed between the photocathode and the focussing electrode.
In British Patent Specification No. 2 171 553 A (Hadland Photonics Limited, inventor Alexander E. Huston) a method of gating such a two mesh streaking or framing image tubes is described. According to Huston the method comprises raising and lowering the potential of the first grid, which is closest to the photocathode, over a short interval of time, to gate the electron beam on and off over the said interval, the second grid being held at a constant potential chosen so that the focussing conditions for the image tube are satisfied.